Conventionally, a developing device detachably attached to an electro-photographic type printer is known. The developing device includes a frame, a developing roller supported to the frame and carrying toner, a thickness regulation blade for regulating a thickness of a toner layer carried on the developing roller, and a seal member preventing toner from leaking from the frame.
A developer cartridge having the thickness regulation blade and the seal member. The thickness regulation blade includes a leaf spring member having generally rectangular shape in front view and a pressing portion provided at a free end portion of the leaf spring member. The seal member is provided with a blade side seal disposed between each widthwise end portion of the leaf spring member and each axial end portion of the developing roller.
The pressing portion is urged toward and in contact with a surface of the developing roller and the blade side seal is in pressure contact with the axial end portion of the developing roller by urging force of the leaf spring member. With this structure, a thickness of the toner layer carried on the surface of the developing roller is regulated, and toner leakage from a gap between the widthwise end portion of the leaf spring member and the axial end portion of the developing roller can be restrained.